Dozens of Boeing 737 Next-Generation aircraft were grounded on Thursday after airlines around the world continued to find cracks in the bodies of their aircraft. The Next-Generation group is a family of aircraft that comprises the Boeing 737-600, -700, -800 and -900, in addition to variants within those types. Sydney-based Qantas Airways became the most recent airline to discover the problems, pulling one of its aircraft out of service before announcing publicly it would conduct thorough inspections of the 32…